Please advise on the problem of soldering pads not sticking to tin during soldering

深圳小花

Please advise on the problem of soldering pads not sticking to tin during soldering [Copy link]

 

邀请：@maychang   @chunyang   @huo_hu   @freebsder   参与回复

There is tin on the soldering iron, but the solder pads on the printed circuit board are not sticky. What is the reason? How to deal with it? Thank you everyone

chunyang

Have you used flux such as rosin? Also observe whether the pad is oxidized and discolored. If so, you need to scrape off the oxide layer first.

maychang

The tin on the soldering iron tip stays in the air for a long time after melting, and the flux (rosin, etc.) on the surface of the tin has become ineffective, causing the surface of the molten tin to oxidize.

How to deal with it? Add a little flux to the welding surface before welding. If you use solder wire, the solder wire itself has flux. When the solder melts, the flux will flow to the welding surface. The solder will then flow to the welding surface. Remove the soldering iron and the welding is completed.

youxiaojie

I learned a lot! I also encountered a similar situation, and now it is much better.

EricCheng

Is the heat dissipated too quickly by the pad?

damiaa

The non-stick soldering pads on the printed circuit board are connected to the large gnd site.

This GND must be made into a pad connected to the ground.

Otherwise, it won't heat up and won't be easy to weld.

Generally, the PCB drawing board will automatically handle this. However, if the pad is added to the large GND later, it is possible that the pad and the ground are directly connected.

eew_1PrAA0

The tin on the tip of the soldering iron stays in the air for too long, and the flux (rosin, etc.) on the surface of the tin is consumed.

dfwisdom

Everyone knows that it is not easy to tin the PCB pads, which will affect the component placement, and indirectly lead to the failure of the subsequent test. Here we will introduce the reasons why the PCB pads are not easy to tin. I hope you can avoid these problems when making and using them, and minimize the losses.

The first reason is: we need to consider whether it is a problem with the customer's design and check whether the connection between the pad and the copper sheet will cause insufficient heating of the pad.

The second reason is: whether there is a problem with the customer's operation. If the welding method is wrong, it will affect the heating power, temperature and contact time.

The third reason is: improper storage.

①Under normal circumstances, the tin-sprayed surface will be completely oxidized in about a week or even shorter.

②OSP surface treatment process can be preserved for about 3 months

③Long-term preservation of immersion gold plate

The fourth reason is: flux problem.

① The activity is not enough to completely remove the oxidized substances on the PCB pad or SMD soldering position.

②The amount of solder paste at the solder joint is insufficient, and the wetting performance of the flux in the solder paste is poor

③ The tin on some solder joints is not full, which may be due to the failure to fully stir the flux and tin powder before use;

The fifth reason is: the problem of the board factory. There is oily substance on the pad that has not been cleaned, and the pad surface is not oxidized before leaving the factory.

The sixth reason is: reflow soldering problem. The preheating time is too long or the preheating temperature is too high, which makes the flux inactive; the temperature is too low or the speed is too fast, so the tin does not melt.

lugl4313820

Use sandpaper, add flux, another reason is that your ferrochrome power is too small.

Ming8686

Have you added flux? Is the pad oxidized?

吾妻思萌

If you are not skilled, just practice more. The formula is not necessarily correct. The soldering iron is hot and the tin wire on the soldering pad is removed.